- The NiCl2·2H2O-Li-arene combination as reducing system. Part 3. Reduction of carbonyl compounds and imines
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The reaction of different carbonyl compounds or their imines with a mixture of nickel(II) chloride dihydrate, an excess of lithium powder and a catalytic amount of naphthalene (16 mol %) or DTBB (8 mol %) in THF at room temperature, leads to the formation of the corresponding alcohols or amines, respectively. The incorporation of deuterium oxide into the nickel salt complex yields the corresponding deuterated products. The process can also be applied to α,β-unsaturated carbonyl compounds leading either to the hydrogenation of only the carbon-carbon double bond or the full hydrogenation, depending on the amount of the nickel salt and/or reaction times.
- Alonso, Francisco,Yus, Miguel
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Read Online
- Extreme thermal stability of disodium 9-fluorenone dianion as a practical indicator for the preparation of absolute THF
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The fact that the lifetime of the disodium 9-fluorenone dianion is longer than that of the corresponding benzophenone dianion in refluxing THF for more than several months, which was proved by their 1H NMR analyses and also by the isolated yields of their oxidation products (parent ketones), strongly suggests using 9-fluorenone as an excellent indicator for the preparation of absolute THF.
- Kamaura, Masahiro,Inanaga, Junji
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Read Online
- Site-selective D2O-mediated deuteration of diaryl alcoholsviaquantum dots photocatalysis
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Owing to the high synthetic value of deuteration in the pharmaceutical industry, we describe herein the conversion of a range of aromatic ketones to deuterium-labeled products in good to excellent yields. Efficient and site-selective deuteration of benzyl alcohols by D2O with visible light irradiation of quantum dots (QDs), together with gram-scale synthesis and photocatalyst recycling experiments indicated the potential of the developed method in practical organic synthesis.
- Li, Xu-Bing,Nan, Xiao-Lei,Tung, Chen-Ho,Wang, Yao,Wu, Li-Zhu
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supporting information
p. 6768 - 6771
(2021/07/13)
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- Light-driven MPV-type reduction of aryl ketones/aldehydes to alcohols with isopropanol under mild conditions
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Alcohols are versatile structural motifs of pharmaceuticals, agrochemicals and fine chemicals. With respect to green chemistry, the development of more sustainable and cost-efficient processes for converting ketones/aldehydes to alcohols is highly desired. Herein, a direct light-driven strategy for reducing ketones/aldehydes to alcohols using isopropanol as the reducing agent and solvent, in the presence of t-BuOLi, under an air atmosphere at room temperature is developed. This operationally simple light-promoted Meerwein-Ponndorf-Verley (MPV) type reduction can be used to produce various benzylic alcohol derivatives as well as applied to bioactive molecules and PEEK model compounds, demonstrating its application potential.
- Cao, Dawei,Xia, Shumei,Pan, Pan,Zeng, Huiying,Li, Chao-Jun,Peng, Yong
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supporting information
p. 7539 - 7543
(2021/10/12)
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- Tunable System for Electrochemical Reduction of Ketones and Phthalimides
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Herein, we report an efficient, tunable system for electrochemical reduction of ketones and phthalimides at room temperature without the need for stoichiometric external reductants. By utilizing NaN3 as the electrolyte and graphite felt as both the cathode and the anode, we were able to selectively reduce the carbonyl groups of the substrates to alcohols, pinacols, or methylene groups by judiciously choosing the solvent and an acidic additive. The reaction conditions were compatible with a diverse array of functional groups, and phthalimides could undergo one-pot reductive cyclization to afford products with indolizidine scaffolds. Mechanistic studies showed that the reactions involved electron, proton, and hydrogen atom transfers. Importantly, an N3/HN3 cycle operated as a hydrogen atom shuttle, which was critical for reduction of the carbonyl groups to methylene groups.
- Chen, Gong,Qiao, Tianjiao,Wang, Yaxin,Zhang, Jian,Zhao, Jianyou
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supporting information
p. 3297 - 3302
(2021/10/14)
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- Practical Method for Reductive Deuteration of Ketones with Magnesium and D2O
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α-Deuterated alcohols have important applications in pharmaceuticals and mechanism studies. Here, we report a new and practical strategy for the reductive deuteration of ketones using a Mg/BrCH2CH2Br/D2O system, which affords α-deuterated alcohols in good yields and with almost quantitative incorporation of deuterium. The synthetic value of this method has been demonstrated by the easy access to deuterated drugs or drug derivatives. This method may inspire the discovery of other deuterium-containing drugs.
- Bao, Hongli,Li, Yajun,Su, Min,Wan, Wen-Ming,Zhu, Nengbo
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supporting information
(2020/02/15)
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- Base-Promoted Aerobic Oxidation/Homolytic Aromatic Substitution Cascade toward the Synthesis of Phenanthridines
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The current protocol represents a transition metal-free synthesis of polysubstituted phenanthridines from abundant starting materials like benzhydrol and 2-iodoaniline derivatives. The reaction involves sequential oxidation of alcohol and direct condensation reaction with the amine resulting in a C?N bond formation followed by a radical C?C coupling in a cascade sequence. The used base potassium tert-butoxide plays a dual role in dehydrogenation and homolytic aromatic substitution reaction. Using this methodology, twenty substituted phenanthridine derivatives were synthesized with up to 85% isolated yield. (Figure presented.).
- Maiti, Debabrata,Halder, Atreyee,De Sarkar, Suman
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supporting information
p. 4941 - 4948
(2019/11/03)
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- Preparation method of deuterated alcohol or amine compound (by machine translation)
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The defects and deficiencies existing in the prior art, are overcome. The invention aims to provide a simple method for producing deuterated alcohols or deuterated amine compounds. The method takes heavy water as a deuterium source, takes ketone or imine
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Paragraph 0099-0104
(2019/10/01)
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- Kinetic studies on tetrabutylammonium bromochromate oxidation of some mono-and di-substituted benzhydrols
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The oxidation of 12 mono- and di-substituted benzhydrols (BH) by tetrabutylammonium bromochromate (TBABC) have been studied in aqueous acetic acid medium. Absence of any effect of added acrylonitrile on the reaction discounts the possibility of a one-electron oxidation, leading to the formation of free radicals. The tetrabutylammonium bromochromate oxidation of 12 mono- and di-substituted benzhydrols complies with the isokinetic relationship and Hammett relationship. The overall mechanism is proposed to involve a cyclic concerted symmetrical transition state leading to the product.
- Hemalatha,Asghar, Basim H.,Mansoor, S Sheik
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p. 821 - 826
(2018/03/13)
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- Regioselective deuteration of alcohols in D2O catalysed by homogeneous manganese and iron pincer complexes
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We report a convenient and cost-effective protocol for the regioselective deuteration of primary and secondary alcohols using Earth abundant homogeneous first row transition metal pincer catalysts. D2O is utilized as both a deuterium source and a solvent, allowing for a benign inexpensive process. Depending on the metal selected (Mn or Fe), a high degree of deuterium incorporation was observed selectively either at the α and β position (Mn) or exclusively at the α position (Fe), for primary alcohols. This simple, efficient, and cost-effective protocol for alcohol C-H bond deuteration constitutes a powerful tool for the large scale synthesis of deuterated molecules.
- Kar, Sayan,Goeppert, Alain,Sen, Raktim,Kothandaraman, Jotheeswari,Surya Prakash
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supporting information
p. 2706 - 2710
(2018/07/05)
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- Correlation analysis and effect of excess free energy of solvents for the kinetics of oxidation of benzhydrol by tetrabutylammoniumbromochromate
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The oxidation of benzhydrol (BH) by tetrabutylammoniumbromochromate (TBABC) was studied in the presence of perchloric acid, in water/organic solvent mixtures of varying excess molar free energy function. The reaction is first order with respect to both TBABC and acid. The reaction rates were determined at different temperatures and the activation parameters computed. A correlation of data with the Kamlet-Taft solvatochromic parameters (α, β, π *) suggests that the specific solute-solvent interactions play a major role in governing the reactivity. The reaction does not induce polymerization of acrylonitrile. The product of oxidation is benzophenone. Based on the kinetic results and product analysis, a suitable mechanism has been proposed for the reaction of TBABC with benzhydrol.
- Hemalatha,Asghar, Basim H.,Sheik Mansoor
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p. 165 - 172
(2020/06/29)
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- Deuterodechlorination of Aryl/Heteroaryl Chlorides Catalyzed by a Palladium/Unsymmetrical NHC System
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The catalytic deuterodechlorination of aryl/heteroaryl chlorides was developed with a palladium/unsymmetrical NHC system, and the precisely controlled introduction of deuterium into a variety of aryl/heteroaryl compounds was achieved with a high level of efficiency, selectivity, and deuteration degree. This method was also successfully applied to the transformation of bioactive agents even in a gram-scale synthesis. The crystal structure analysis of Pd-NHC complexes led to the observation of Pd-arene interaction.
- Kuriyama, Masami,Hamaguchi, Norihisa,Yano, Gemba,Tsukuda, Kotaro,Sato, Kanako,Onomura, Osamu
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p. 8934 - 8946
(2016/10/14)
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- Magnesium-Alkoxide directed photoaddition of tetrahydrofurans to γ,γ-disubstituted allylic alcohols
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Magnesium-Alkoxide directed photoaddition of tetrahydrofurans to γ,γ-disubstituted allylic alcohols was achieved. When the allylic alcohols were treated with Grignard reagent in THF under light, the corresponding γ-(2-Tetrahydrofuryl) substituted alcohols
- Watanabe, Yasutaka,Sakai, Takahiro,Maeda, Hajime,Segi, Masahito,Soeta, Takahiro,Ukaji, Yutaka
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p. 833 - 844
(2017/04/10)
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- Stainless-Steel Ball-Milling Method for Hydro-/Deutero-genation using H2O/D2O as a Hydrogen/Deuterium Source
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A one-pot continuous-flow method for hydrogen (deuterium) generation and subsequent hydrogenation (deuterogenation) was developed using a stainless-steel (SUS304)-mediated ball-milling approach. SUS304, especially zero-valent Cr and Ni as constituents of the SUS304, and mechanochemical processing played crucial roles in the development of the reactions.
- Sawama, Yoshinari,Kawajiri, Takahiro,Niikawa, Miki,Goto, Ryota,Yabe, Yuki,Takahashi, Tohru,Marumoto, Takahisa,Itoh, Miki,Kimura, Yuuichi,Monguchi, Yasunari,Kondo, Shin-Ichi,Sajiki, Hironao
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p. 3773 - 3776
(2015/12/08)
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- A novel lanthanum metal-assisted reaction of diaryl ketones and electrophiles
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A novel and efficient lanthanum metal-assisted carbon-carbon bond formation of diaryl ketones and various electrophiles, such as carbonyl compounds, esters, nitriles, and epoxides, has been developed. When diaryl ketones were allowed to react with dialkyl ketones in the presence of lanthanum metal and a catalytic amount of iodine, the cross pinacol coupling reaction proceeded to give the corresponding unsymmetrical 1,2-diols in moderate to good yields. α-Hydroxy ketones were prepared by the lanthanum metal-assisted reaction of diaryl ketones with esters or nitriles, followed by hydrolysis with aq HCl. It is interesting to note that for the epoxides, the coupling reaction proceeded via the Meinwald rearrangement of epoxides to give the corresponding 1,2-diols.
- Umeda, Rui,Ninomiya, Masashi,Nishino, Toshiaki,Kishida, Makoto,Toiya, Shunsuke,Saito, Tomoki,Nishiyama, Yutaka,Sonoda, Noboru
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p. 1287 - 1291
(2015/03/05)
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- Ruthenium(II) picolyl-NHC complexes: Synthesis, characterization, and catalytic activity in amine N-alkylation and transfer hydrogenation reactions
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Ruthenium(II) p-cymene complexes with picolyl-functionalized N-heterocyclic carbenes [(η6-p-cymene)Ru(L)(Cl)][PF6] (L = 3-methyl-1-(2-picolyl)imidazol-2-ylidene (1a), 3-isopropyl-1-(2-picolyl) imidazol-2-ylidene (1b), 3,4,5-trimethyl-1-(2-picolyl)imidazol-2-ylidene (1c), 3-mesityl-1-(2-picolyl)imidazol-2-ylidene (1d), 3-methyl-1-(2-picolyl) benzoimidazol-2-ylidene (1e), 3-methyl-1-(2-picolyl)-4,5-dichloroimidazol-2- ylidene (1f), 3-phenyl-1-(2-picolyl)imidazol-2-ylidene (1g)) have been synthesized and characterized. Compounds 1a-g were recrystallized, and X-ray crystal structures are reported for 1a,f. Furthermore, compounds 1a-f show catalytic activity in transfer hydrogenation of ketones and N-alkylation of amines. Notably, complexes 1a,c,f were found to be very efficient and versatile catalysts toward transfer hydrogenation of a wide range of ketones and imines in addition to N-alkylation of several amines.
- Fernandez, Francys E.,Puerta, M. Carmen,Valerga, Pedro
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p. 6868 - 6879
(2012/11/13)
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- Metal amidoboranes: Superior double-hydrogen-transfer agents in the reduction of ketones and imines
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Metal amidoboranes (MABs), such as lithium amidoborane (LiAB), show superior ability in reducing ketones and imines directly into their corresponding secondary alcohols and amines, respectively, at room temperature with high conversion and yields. A mechanistic study indicates that the reduction proceeds through a double-hydrogen-transfer process. Both protic H(N) and hydridic H(B) protons in the amidoborane participate in the reaction. Theoretical investigations show that the first (and rate-determining) step of the reduction reaction is the elimination of LiH from LiAB, followed by the transfer of H(Li) to the C site of the unsaturated bond. Copyright
- Xu, Weiliang,Wu, Guotao,Yao, Wei,Fan, Hongjun,Wu, Jishan,Chen, Ping
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supporting information
p. 13885 - 13892
(2013/01/15)
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- Enantioselective catalytic α-alkylation of aldehydes via an S N1 pathway
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Primary aminothiourea derivatives are shown to catalyze enantioselective alkylation of α-arylpriopionaldehdyes with diarylbromomethane. Evidence for a stepwise, S N1 mechanism in the substitution reaction induced by anion binding to the catalyst is provided by catalyst structure-activity studies, kinetic isotope effects, linear free-energy relationship studies, and competition experiments.
- Brown, Adam R.,Kuo, Wen-Hsin,Jacobsen, Eric N.
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supporting information; experimental part
p. 9286 - 9288
(2010/11/03)
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- Direct access to ketones from aldehydes via rhodium-catalyzed cross-coupling reaction with potassium trifluoro(organo)borates
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A direct cross-coupling reaction of aromatic aldehydes with potassium trifluoro(organo)borates afforded ketones in high yields and under mild conditions in the presence of a rhodium catalyst and acetone. This new reaction, involving a formal aldehyde C-H bond activation, is believed to proceed via a Heck-type mechanism followed by hydride transfer to acetone. Copyright
- Pucheault, Mathieu,Darses, Sylvain,Genet, Jean-Pierre
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p. 15356 - 15357
(2007/10/03)
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- Reduction of carbonyl compounds and imines using the CuCl2·2H2O-Li-DTBB (Cat.) combination
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The reaction of different carbonyl compounds and imines with a mixture of copper(II) chloride dihydrate, an excess of lithium sand, and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5 mol%) in THF at room temperature, led to the formation of the corresponding alcohols and amines, respectively. The process was also applied to the transformation of α,β-unsaturated carbonyl compounds into the corresponding saturated alcohols. The use of the deuterated copper salt CuCl2·2D2O allowed the preparation of the corresponding deuterated products.
- Alonso, Francisco,Vitale, Cristian,Radivoy, Gabriel,Yus, Miguel
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p. 443 - 447
(2007/10/03)
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- Mechanisms for the oxidation of secondary alcohols by dioxoruthenium(VI) complexes
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Possible mechanisms for the oxidation of alcohols by dioxoruthenium(VI) complexes are critically evaluated. Rate constants for the reduction of trans-[(TMC)Ru(VI)(O)2]++ (TMC = 1,4,8,11-tetramethyl-1,4,8,11- tetraazacyclotetradecane) by substituted benzhydrols are correlated more satisfactorily with Hammett σ substituent constants (p = -1.44 ± 0.08, r2 = 0.98) than with σ+ substituent constants (ρ = -0.72 ± 0.11, r2 = 0.83). Similar observations for the oxidation of substituted benzyl alcohols have recently been reported, confirming that the transition state for these reactions is not carbocation-like. Primary deuterium isotope effects indicate that cleavage of the α-C-H bond is rate-limiting. The lack of an observable O-D isotope effect and the ease of oxidation of ethers indicates that the presence of a hydroxyl is not essential. The previously reported observation that cyclobutanol is quantitatively converted into cyclobutanone by dioxoruthenium(VI) complexes eliminates free-radical intermediates from consideration as part of the mechanism, and negative entropies of activation (-ΔS(+) = 96-137 J mol-1 K-1) suggest a structured transition state. Only two of eight possible reaction mechanisms considered were found to be consistent with the available data. A critical analysis of the available data indicates that a 2 + 2 (C - H + Ru = O) addition and a reaction initiated by ligand formation through the interaction of the reductant's HOMO with the oxidant's LUMO are the most likely reaction mechanisms.
- Wang, Zhao,Chandler, W. David,Lee, Donald G.
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p. 919 - 928
(2007/10/03)
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- Photoreduction of chloranil by benzhydrol and related compounds. Hydrogen atom abstraction vs sequential electron-proton transfer via quinone triplet radical ion-pairs
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The photoreduction of chloranil (Q) to the hydraquinone (QH2) in benzene by benzhydrols and by related arylmethanols has been investigated. The products of photooxidation of the benzhydrols are benzophenones, in lieu of formation of benzpinacols. Three distinct mechanisms of oxidation-reduction have been identified from quantum yield determinations and laser flash photolysis experiments, including quinone triplet quenching via H-atom and electron transfer paths. Direct excitation of ground state quinone complexes has also been investigated. The quenching of the triplet state of the quinone by benzhydrol proceeds normally (k(q) = 1.3 x 106 M-1 s-1) and gives semiquinone radical (QH., λ(max) = 435 nm) and the benzhydryl radical (λ(max) = 535 nm). The latter intermediate decays by pseudo-first-order kinetics through hydrogen atom transfer with ground state quinone (Q). Triplet quenching by bis(4-methoxyphenyl)methanol proceeds at a more rapid rate (k(q) = 5.5 x 109 M-1 s-1) leading to an intermediate that is identified as the chloranil radical anion (λ(max) = 450 nm). A similar intermediate is observed on Q quenching by 1-naphthylmethanol and acenapthenol with the appearance of an accompanying naphthalene radical cation absorption (ca. 670 nm). The radical ion transients, which are assigned to contact ion-pairs (triplet excited complexes) of the quinone and the various electron donors, decay to semiquinone radicals (QH.) by first-order processes occurring in the 100 ns time regime. The transient behavior is interpreted in terms of a hydrogen atom transfer mechanism for photoreduction with benzhydrol and, for the more robust electron donors, a mechanism involving electron transfer followed by proton transfer between geminate radical ions. For the electron transfer donors, ground state charge-transfer (CT) complexes can be observed (λ(max) ca. 500 nm). Selective CT excitation leads to quinone photoreduction with reduced quantum yield. The results are discussed in terms of the time resolution of sequential electron/proton transfer steps for photogenerated ion-pairs, the occurrence of one photon-two electron transfer photoredox mechanisms and the kinetically distinct pathways for decay of singlet and triplet intimate radical ion-pairs.
- Jones II, Guilford,Mouli, Nandini,Haney, William A.,Bergmark, William R.
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p. 8788 - 8794
(2007/10/03)
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- Reduction of Ag(I) by 1-acyl-2-arylhydrazines: Mechanism of photographic infectious development
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The photographic process of 'infectious development' in which 1-acyl-2-arylhydrazines reduce Ag(I) has been studied using analogues. 1-Acyl-2-aryldiazenes, resulting from oxidation of 1-acyl-2-arylhydrazines, are hydrolysed to anions of aryldiazenes (ArN = NH), which undergo further oxidation with loss of nitrogen to yield aryl radicals. The aryl radicals cause 'feedback inhibition' which is prevented by the addition of benzhydrol.
- Bowman, W. Russell,Forshaw, J. Anthony,Hall, Kevin P.,Kitchin, Jonathan P.,Mott, Andrew W.
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p. 3961 - 3972
(2007/10/03)
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- C-C Bond Cleavage in O-Centered Mono- and Dianions Derived from α-Dicarbonyl Compounds
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The reaction of organolithium compounds with oxalyl derivatives and cyclic 1,2-dicarbonyl compounds leads to pinacols or ketones derived from homolytic C-C bond cleavage of the intermediate O,O-centered pinacol dianions depending on the ability of the substituents for the stabilisation of the resulting radical anion.The homolysis is induced by electrostatic repulsion of the negatively charged oxygen atoms.
- Varea, Teresa,Medio, Mercedes,Ballesteros, Rafael,Oniga, Ovidiu,Asensio, Gregorio
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p. 10093 - 10100
(2007/10/02)
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- The Use of Chemical Probes To Differentiate between Polar and SET-Hydrogen Atom Abstraction Pathways Involved in the Reduction Reaction Promoted by an 8-Al-4 Anion
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The mechanism for the reduction of aromatic ketones and alkyl halides with lithium tetrakis(N-dihydropyridyl)aluminate was found to proceed competitively by hydride reduction and by single electron transfer (SET)-hydrogen atom abstraction processes.A series of ketyl fragmentation probes were used to differentiate the two pathways.A SET process is the dominant pathway when the ketones involved are sterically hindered or when strong electron acceptors are used as the substrates.The observation that EPR-active intermediates can be detected, or that small amounts of radical derived products are formed, demonstrates only that a SET pathway is available but cannot be used to establish the mechanism of the major product-forming reactions.
- Tanner, Dennis D.,Yang, C. M.
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p. 5907 - 5914
(2007/10/02)
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- α-Oxygen-Substituted Organolithium Compounds and their Carbenoid Nature: Reactions with RLi and Other Nucleophiles, Experimental and IGLO-Calculated 13C-NMR Shifts of the Carbenoid C Atom
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In addition to the earlier demonstrated C-O bond elongation between the anionic carbon atom and oxygen in α-lithiated ethers which indicates a carbenoid character of these compounds we provide further evidence for this property in this publication.Thus, α
- Boche, Gernot,Bosold, Ferdinand,Lohrenz, John C. W.,Opel, Achim,Zulauf, Peter
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p. 1873 - 1886
(2007/10/02)
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- Evidence for rate limiting C-H bond cleavage in the leuckart reaction
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A rho value of +0.21 is reported for the reaction of mono 4-substi- tuted benzophenones with formamide. This, in conjunction with a kinetic iso- tope effect value of 1.80 obtained for the system, suggests a rate-limiting C-H bond cleavage.
- Awachie, Peter I.,Agwada, Vincent C.
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p. 1899 - 1910
(2007/10/02)
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- Photochemical Reaction between 1,4-Naphthalenedicarbonitrile and α-Substituted Benzylic Derivatives
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The photochemical reaction of 1,4-naphthalenedicarbonitrile (NDN) with benzylic derivatives of the general formula PhCHRX (R = H, Ph; X = H, C, O, S, Si, Sn-bonded substituents) has been investigated.The competition between C-H and C-X bond cleavage in the photochemically created radical cation PhCHRX(.+) is revealed by the different chemical products formed, viz. 5,11-methanodibenzocyclooctenes (2), from proton transfer and coupling of the radicals within the cage, and 2-benzyl- (3) and 1-benzyl-1,2-dihydronaphthalenes (4), as well as 4-benzyl-1-naphthalenenitriles (5), from the reaction between the radical anion NDN(.-) and the neutral radicals PhCHR(.) or PhCRX(.).With the alcohols, the hydroxylic proton is easily transferred.Measurement of reaction quantum yield and fluoroscence quenching and thermochemical calculations support the mechanism proposed.
- Sulpizio, Ada,Albini, Angelo,d'Alessandro, Nicola,Fasani, Elisa,Pietra, Silvio
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p. 5773 - 5777
(2007/10/02)
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- Nucleophilic Addition of Lanthanoid Metal Umpoled Diaryl Ketones to Electrophiles
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Ytterbium metal promoted cross-coupling reactions of diaryl ketones with a variety of electrophiles are described.Diaryl ketones treated with 1-2 equiv of Yb metal react smoothly with other ketones, nitriles, epoxides, CO2, etc., to give the corresponding unsymmetrical pinacols, α-hydroxy ketones, 1,3-diols, α-hydroxy carboxylic acids, etc., in good yields respectively.These reactions occur via nucleophilic addition of the intermediates 4a-c to electrophiles.Reaction of benzophenone (1a) with Yb metal is discussed in detail and some information on the composition of the intermediates of the reaction of diaryl ketones with Yb metal are also given.
- Hou, Zhaomin,Takamine, Kan,Aoki, Osamu,Shiraishi, Hiroyuki,Fujiwara, Yuzo,Taniguchi, Hiroshi
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p. 6077 - 6084
(2007/10/02)
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- Ytterbium Metal Mediated Synthesis of Symmetrical and Unsymmetrical Pinacols from Carbonyl Compounds
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Reaction of aromatic aldehydes and ketones with ytterbium metal gives the corresponding pinacols in high yields.Cross-coupling reaction of benzophenone with other carbonyl compounds to produce unsymmetrical pinacols is also described.
- Hou, Zhaomin,Takamine, Kan,Fujiwara, Yuzo,Taniguchi, Hiroshi
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p. 2061 - 2064
(2007/10/02)
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- Chemistry of Organolanthanoids. Lanthanoid-Mediated C-C Bond Formation and Cleavage and C-C Double Bond Reduction
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Reactions of the organolanthanoid ?-complexes RLnI with α,β-unsaturated carbonyl compounds and allylic alcohols under various conditions are described.An equivalent of RYbI reacts with α,β-unsaturated carbonyl compounds to give 1,2-addition products 1 regioselectively.On the other hand, the reaction of an excess of RYbI with chalcone gives C-C bond cleavage products 2 and 4 and deoxygenation product 3 instead of 1.In the reactions of PhYbI with benzalacetone or cinnamyl alcohol, compounds 5, derived from addition of RYbI to the C-C double bonds of the substrates, are obtained as main products.An excess of PhEuI reacts with α,β-unsaturated carbonyl compounds to give 2-4.C-C double bonds conjugated with phenyl group are hydrogenated by PhYbI/MeOH.Reduction of trans-stilbene with Yb/MeOD gives the deuteriated product 6a.
- Hou, Zhaomin,Fujiwara, Yuzo,Jintoku, Tetsuro,Mine, Norioki,Yokoo, Kazuhiro,Taniguchi, Hiroshi
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p. 3524 - 3528
(2007/10/02)
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- Aspects of the Chemistry of Donor Solvent Coal Dissolution Reactions. The Reduction of Benzophenone and the Diproportionation of Benzhydrol in Hydrocarbon Solvents at High Temperature
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The reduction of benzophenone by hydrogen donor molecules such as tetralin and dihydroanthracene to give diphenylmethane was investigated in the temperature range 300-400 deg C.Several lines of evidence indicate that the reaction occurs in three distinct stages.The first stage is a radical process which gives benzhydrol.In the second stage, this intermediate undergoes an SN reaction to produce water and bis(diphenylmethyl) ether.The ether disproportionates in a readily initiated, free radical chain reaction to give diphenylmethane and benzophenone.
- Choi, Chol-yoo,Stock, Leon M.
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p. 2871 - 2875
(2007/10/02)
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- Carbanion Rearrangements by Intramolecular 1,ω Proton Shifts, IV. The Reaction of ω,ω-Diphenylalkyllithium Compounds: Proof for an Intramolecular Transmetallation Reaction by Crossover Experiments Using Isotopic Labelled Starting Material
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3,3-Diphenylpropyllithium (2) and 2-(9-fluorenyl)ethyllithium (43) do not show a 1,3 proton shift but splitt off ethylene.On the other hand 4,4-diphenylbutyllithium (19) in diethyl ether can be forced to rearrange to 1,1-diphenylbutyllithium (18) by the addition of THF.The half reaction time for this 1,4 proton shift was found to be about 4 minutes.Proof for the intramolecular character of this transmetallation reaction was obtained by crossover experiments with specifically deuterated starting material.The 1,5 proton shift with 5,5-diphenylpentyllithium (12) occurs considerably slower than the 1,4 shift with 4,4-diphenylbutyllithium (19).The rearrangement also takes place in pure diethyl ether although with a half reaction time of about 2 days.Only 3-(9-fluorenyl)propyllithium (41) in diethyl ether spontaneously shows rearrangement already at -30 deg C, whereby 9-propyl-9-fluorenyllithium (42) is formed by a 1,4 proton shift.A 1,ω phenyl migration according to Grovenstein-Zimmerman in no case could be observed.
- Maercker, Adalbert,Passlack, Michael
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p. 710 - 723
(2007/10/02)
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- Oxidation of Diphenylmethanol by Bromamine T. A Kinetic and Mechanistic Study
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Bromamine T (BAT) oxidises diphenylmethanol and substituted diphenylmethanols smoothly and quantitatively to the respective benzophenones in aquoeus acetic acid.Mineral acids catalyse the reaction and the rate law is found to be -d/dt=k+>.The reaction is characterised by the absence of any kinetic isotope effect and a break in the Hammett plot with ρ values of -4.2 and -0.4 for the two limbs.Three alternative mechanistic pathways have been proposed involving (i) diphenylmethyl cation, (ii) a 'phenonium ion' type intermediate from the decomposition of the alkyl hydrobromite ester, or (iii) ipso substitution at the benzene ring followed by dehydrobromination and aromatization.
- Gunasekaran, Somasundaram,Venkatasubramanian, Nagaswami
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p. 949 - 954
(2007/10/02)
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- Kinetics and Mechanism of Reaction of 1-Chlorobenztriazole with Diphenylcarbinol in Acidic Media
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Oxidation of diphenylcarbinol by 1-chlorobenztriazole (CBT) in the presence of mineral acids, affords 4(7)-(chlorodiphenylmethyl)benzotriazole (II) as the product instead of the expected benzophenone.In the formation of II, it is believed that benzotriazole undergoes an electrophilic attack by Ph2CH+ followed by rearrangement to give II.The rate-law for the reaction has been found to be, rate = kobs +>2.The plot of log kobs against ?+ is a scatter.The effect of substituents on the rate of oxidation of diphenylcarbinol with CBThas been studied by introducing substituents in the benzene ring of benzotriazole moiety.The reaction of 4,5,6,7-tetrachloro-1-chlorobenzotriazole (TCCBT) and 4-nitro-1-chlorobenzotriazole (NCBT) with diphenylcarbinol affords benzophenone.These reactions are characterized by negligible kinetic isotopic effects.
- Rangadurai, A.,Srinivasan, V. S.,Thiagarajan, V.,Venkatasubramanian, N.
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p. 898 - 903
(2007/10/02)
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- Kinetic Hydrogen Isotope Effects in Intermolecular Hydride Transfer from Arylalkanes to 9-Arylfluoren-9-yl Cations
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Rates of hydride-ion transfer to a series of 9-phenylfluoren-9-yl cations, substituted in the phenyl group, from triphenylmethane and 4,4'-dimethoxydiphenylmethane have been measured at 30 degC in trifluoroacetic acid solution containing 6percent v/v acet
- Bethell, Donald,Hare, Gerard J.,Kearney, Paul A.
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p. 684 - 691
(2007/10/02)
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- Kinetics of Oxidation of Benzhydrols by Aqueous Chlorine
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The kinetics of oxidation of benzhydrol by aqueous chlorine have been studied in aqueous acetic acid media.The rate law is found to be -d/dt = k.The rate law, kinetic isotope effect, the effect of chloride ion, and the substituent effect on the rate are consistent with a mechanism in which abstraction of the α-hydrogen as hydride ion by molecular chlorine has no rate determining function.
- Gopalakrishnan, Ganesa,Babu, M. E. Prabakara,Pai, B. R.
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p. 998 - 1001
(2007/10/02)
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